Four years after Mayor Thomas M. Menino expressed concerns about arming more Boston police with military-style rifles, the department is quietly preparing to train 99 patrol officers to use such semiautomatic rifles, a dramatic boost in firepower that some officials say is excessive.

Under the plan, 22 uniformed officers on every shift — two for each of the city’s 11 districts — would have routine access to the weapons in their cruisers after they are trained. It represents a substantial increase from the current complement of four to eight specialized officers who patrol the city in “gun cars” equipped with an M4 semiautomatic rifle and a shotgun.

It is one of the final policy changes instituted by Commissioner Edward F. Davis, who left the department Friday after nearly seven years at the helm.

“It’s standard operating procedure across the nation, and the officers have to be able to protect themselves,” Davis said in an interview last week. “I think it’s a practical and appropriate plan.”

Davis said officials had been planning the change months before the April 15 Boston Marathon terrorist attacks, but the tragedy underscored the need for a greater number of more powerful weapons.

“An incident like that reinforces the need for equipment that’s necessary to defend the community,” he said.

The new mayor would have to approve a budget request for the new rifles, which could cost about $2,500 each, plus $500 for ammunition.

But some officials within the Police Department said they have serious misgivings about providing so much firepower to dozens of officers and worry how residents in neighborhoods where police are already viewed suspiciously might react.

“It’s almost like we’re moving away from being community policing officers to being Navy SEALs,” said Jack Kervin, president of the Boston Police Superior Officers Federation. “Is this Davis’s legacy?”

In 2009, Boston police were slated to receive 200 M-16s from the US military and had planned to train dozens of patrol officers and members of specialized units such as the bomb squad and the harbor patrol to use the weapons. But the department canceled the shipment after the plan fell through.

At the time, police cited the shootings at Columbine High School in 1999, when first responders had to wait for specialized teams to arrive as two teenage shooters killed schoolmates inside.

Police also reasoned that semiautomatic rifles allow officers to halt criminals armed with potent firepower from greater distances and more accurately.

But the plan died after Menino said he was uncomfortable with it.

“I would not want them on regular patrols,” he said at the time. “Maybe on specialized units, at special times, yes.”

Menino would not comment directly on the new plan, but his office released a statement saying that he supports the department’s strategies.

“The mayor made clear that he doesn’t expect these types of weapons to be used regularly, but rather stored securely in police vehicles and used only during necessary emergency situations,” reads the statement issued by a spokeswoman. “He is well aware that they are common in other jurisdictions and will continue to advocate for the limited use of these weapons for routine work.”

Nationwide, more police departments in major cities and small towns have been arming patrol officers with such rifles, arguing that they need the weapons to counter illegal, military-style weapons on the street.

In Massachusetts, 87 police departments have a total of 918 semiautomatic rifles in their arsenal.

In Boston, district officers carry .40-caliber handguns and shotguns that fire bean-bag rounds, which are designed to deliver a blow but not penetrate the body.

In one of his last acts as commissioner, Davis told officers who want semiautomatic rifle training to state their interest to their district commander by Nov. 1.

Superintendent in Chief Daniel Linskey said it was not immediately clear how many officers had applied for the training, but he said there is a lot of interest from patrol officers.

The department still has to negotiate the new policy with the four police unions, but Linskey said officials are close to reaching an agreement with the patrol officers union.

Thomas Nee, president of the Boston Police Patrolmen’s Association, could not immediately be reached for comment.

The department wants supervisors to carry the weapons, as well, but it is not clear how many would need to be trained.

Kervin said he is worried about the added burden the additional weapons would place on supervisors.

He said that the department should consider placing more of the specialized gun cars on the street, rather than arming more officers.

In 2009, as word got out about the Police Department’s plans, members of the community resisted. “I think people thought we were going to be responding to 911 calls across the city with these,” Linskey said.

This time, officials have briefed religious and community leaders who work in the city’s more troubled neighborhoods, Linskey said.

One of those leaders, Jorge Martinez — executive director of Project RIGHT, a nonprofit in the Grove Hall section of Roxbury — was fiercely critical of the idea in 2009, calling it a ridiculous attempt to arm officers with “toys.”

He said he feels differently now.

“Given the complexities of folks who are violent and who have access to assault weapons,” he said, “I think it would be in the police’s best interest to have trained officers [with] access to assault weapons.”

Linskey said he understands there is delicate balance between arming officers with heavier firepower and assuring the public that the department is not becoming militarized.

“We have to weigh those two,” Linskey said. “We unfortunately live in a world where this has become a reality.”

Linskey described the department’s new weapons, which he called “patrol rifles,’’ as “in the style of the AR-15,” which is the most popular type of semiautomatic gun in the United States.

Linksey said SWAT teams need more backup, pointing to the aftermath of the April 15 Marathon bombing, when officers who had tracked down the bombing suspects in Watertown believed they were armed with semiautomatic rifles.

Boston police officers who responded during those first terrifying moments had to remove the bean bags from their shotguns, then wait for shotgun shells to be brought to the scene, Linskey said.

“We had to convert on the fly,” he said. “We didn’t have enough” weapons.

The department wants to add 33 semiautomatic rifles to supplement the more than 60 SWAT team officers who use M4 rifles, Linskey said.

The department eventually wants to bring in more shotguns, but the immediate goal is to arm patrol officers with the rifles.

The goal is to train enough officers so that two officers on every shift are armed with the weapons, which would be kept in a locked box in their cruiser. When not being used on the shift, the guns would be stored in a secure district locker.

Under a draft of the new policy obtained by the Globe, a patrol officer would use a shotgun or a semiautomatic rifle for the following reasons:

A suspect is armed with a deadly weapon and poses an immediate lethal threat; the distance between the suspect and the officer is too great for a service pistol to be effective; the suspect is wearing body armor or protected by material that cannot be penetrated with a service pistol; the suspect is heavily armed or is using sophisticated weapons, like long guns or explosives; and the officer is facing a dangerous animal, such as a rabid coyote, that needs to be killed or stopped from a safe distance.

Nancy Robinson — executive director of Citizens for Safety, a nonprofit group that advocates for more gun control — said that “arming police with high-powered weapons is not the only solution” and that Congress should pass federal safeguards to prevent illegal guns from getting to the street in the first place.

“Until we get serious about curbing gun trafficking in this country, we’re forcing police departments into an arms race with criminals,” she said.